Descripción

This device is an 8-bit non-inverting level translator which uses two separate configurable power-supply rails. The A port tracks the VCCA pin supply voltage. The VCCA pin accepts any supply voltage between 1.4V and 3.6V. The B port tracks the VCCB pin supply voltage. The VCCB pin accepts any supply voltage between 1.65V and 5.5V. Two input supply pins allows for low Voltage bidirectional translation between any of the 1.5V, 1.8V, 2.5V, 3.3V, and 5V voltage nodes.
When the output-enable (OE) input is low, all outputs are placed in the high-impedance (Hi-Z) state.
To put the device in the Hi-Z state during power-up or power-down periods, tie OE to GND through a pulldown resistor. The current-sourcing capability of the driver determines the minimum value of the resistor.

 

Características

• No direction-control signal needed
• Maximum data rates:
–110Mbps (push pull)
–1.2Mbps (open drain)
• 1.4V to 3.6V on A port and 1.65V to 5.5V on B port (VCCA ≤ VCCB)
• No power-supply sequencing required – either VCCA o VCCB can be ramped first
• Latch-up performance exceeds 100mA per JESD 78, class II
• ESD protection exceeds JESD 22 (A port):
–2000 V Human Body Model (A114-B)
–150 V Machine Model (A115-A)
–1000 V Charged-Device Model (C101)
• IEC 61000-4-2 ESD (B-port):
–± 8kV Contact Discharge
–± 6kV Air Discharge

 

Aplicaciones

• Handsets
• Smartphones
• Tablets
• Desktop PCs

 

Visión general

The TXS0108E device is a directionless voltage-level translator specifically designed for translating logic voltage levels. The A-port accepts I/O voltages ranging from 1.4V to 3.6V. The B-port accepts I/O voltages from 1.65V to 5.5V. The device uses pass gate architecture with edge rate accelerators (one shots) to improve the overall data rate. The pull-up resistors, commonly used in open-drain applications, have been conveniently integrated so that an external resistor is not needed. While this device is designed for open-drain applications, the device can also translate push-pull CMOS logic outputs.

 

Output Load Considerations

TI recommends careful PCB layout practices with short PCB trace lengths to avoid excessive capacitive loading and so that proper one-shot triggering takes place. PCB signal trace-lengths should be kept short enough such that the round trip delay of any reflection is less than the one-shot duration. This improves signal integrity by allowing any reflection to see a low impedance at the driver. The one-shot circuits have been designed to stay on for approximately 30ns. The maximum capacitance of the lumped load that can be driven also depends directly on the one-shot duration. With very heavy capacitive loads, the one-shot can time-out before the signal is driven fully to the positive rail. The one-shot duration has been set to best optimize trade-offs between dynamic ICC, load driving capability, and maximum bit-rate considerations. Both PCB trace length and connectors add to the capacitance of the TXS0108E output. Therefore, TI recommends that this lumped-load capacitance is considered to avoid one-shot retriggering, bus contention, output signal oscillations, or other adverse system-level affects.

 

Pull-up or Pull-down Resistors on I/O Lines

The TXS0108E has the smart pull-up resistors dynamically change value based on whether a low or a high is being passed through the I/O line. Each A-port I/O has a pull-up resistor (RPUA) to VCCA and each B-port I/O has a pull-up resistor (RPUB) to VCCB. RPUA and RPUB have a value of 40kΩ when the output is driving low. RPUA and RPUB have a value of 4kΩ when the output is driving high. RPUA and RPUB are disabled when OE = Low. This feature provides lower static power consumption (when the I/Os are passing a low), and supports lower VOL values for the same size pass-gate transistor, and helps improve simultaneous switching performance.

 

Device Functional Modes

The TXS0108E device has two functional modes, enabled and disabled. To disable the device set the OE pin input low, which places all I/Os in a high impedance state. Setting the OE pin input high enables the device.